The Orioles won the opener 7-5, rallying from a four-run deficit behind Nolan Reimold, who homered and hit a tiebreaking two-run double in the eighth inning.
Los Angeles has lost six straight, its longest skid since a seven-game slide last June. The Dodgers will complete their first series in Baltimore since 2002 on Sunday, looking to avert a sweep.
Chen (1-2) allowed one run, walked four and struck out two to end a six-game losing streak dating back to Aug. 19, 2012.
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